1. Technical Field
The present invention relates to a communication device and method; in particular, a communication device and method having a plurality of processors and applications using a shared memory.
2. Discussion of Related Art
Recent advances in semiconductor, wireless, and software technologies make available a multitude of applications operable from mobile communication devices such as cellular phones and PDAs. For example, handheld phones used for wireless communication are also usable as PDAs, cameras, game play devices, etc. These applications were available previously as separate standalone devices. In these multi-application communication devices, there are usually at least two integrated circuit chips, each with one or more processing devices. One of the two chips serves as a modulator/demodulator (“modem”). The modem chip includes a digital signal processor (“DSP”) for signal processing purposes to effect wireless communications with base stations or other communication devices. The other chip is an application processor (“AP”), having a central processing unit (“CPU”) to operate functions and peripherals such as camera or image capture, display, 2D/3D engine/memory, database, etc. Because each application or peripheral operates with a different platform, the CPU communicates with each of the applications and peripherals through interfaces which are distinct and specific to the respective application. The different interfaces are usually embedded within the AP chip. Each of the AP and modem chips in the communication device has respective local memory devices (RAMs and ROMs) for data and program storage, controlled by its respective processor. Each of the AP and modem chips also runs its respective operating system or platform. Communications between the AP and the modem chips are made through a shared interface memory and respective interfaces.
FIG. 1 shows a simplified block diagram of a conventional communication device having the above described configuration, with a modem chip and an application processor chip for operating application or peripheral devices such as a camera, an LCD display, local memory RAM and ROM. A dual-port SRAM serves as the shared interface memory for facilitating communication between the AP and modem chips. Each chip has its respective memory controllers for controlling the local RAM and ROM and the shared interface memory.
FIG. 2 shows a more detailed block diagram of the conventional communication device of FIG. 1. As shown, the AP chip 110 includes a CPU 111 for controlling peripheral devices such as LCD module 120, camera module 130, and memory module 140. Because each application/peripheral has its own operating system, there must be separate interfaces or control units for respective applications, such as LCDC 113 for controlling the LCD module 120, CAM controller 115 for controlling the camera module 130, and memory controller 117 for controlling memory module 140. Further, each application connects to the AP chip 110 through different buses at different pinouts of the chip. As an example, the LCD module 120 requires a 30-pin bus connection to the LCDC 113, the camera module 130 requires a 20-pin bus connection to camera control unit 115, and the memory module 140 requires a 50-pin bus connection to memory controller 117.
The modem chip 150 includes a DSP 155 and coprocessor 151 for effecting radio communication functions. The DSP 155 communicates with coprocessor 151 through internal interface 153. The modem chip 150 connects to an external memory module 160 via a memory controller 157. Communication between the AP chip 110 and modem chip 150 is by interface line 170, via a shared memory (not shown). Individual memory controllers 119 and 159 are disposed within respective AP chips 110 and modem chip 150 to independently access through respective ports of the dual port shared interface memory.
In mobile devices such as a cellular phone with multiple applications such as that shown in FIGS. 1 and 2, the physical size of the AP chip 110 is comparatively large because of the requirement for the large number of pinouts and the different busses and interfaces. Also, operation of multiple applications with different platforms requires constant processing by the CPU 111, therefore, power consumption would be relatively high. Even if the AP and modem chips were operating under a common platform, such as disclosed in the commonly assigned U.S. patent application Ser. No. 10/813,327, filed on Mar. 30, 2004, the disclosure of which is incorporated-by-reference in its entirety herein, the separate local RAM and ROM devices in respective AP and modem chips still represent duplication of resources.
A need therefore exists for a mobile communication device and method having multiple applications which minimizes physical size and power consumption.